333 Series Hi-Flow Balanced Sleeve Thermostat

The Robertshaw 333 Series thermostat is a specialized component designed to work with the 351 Cleveland Controlled bypass system, offering a unique solution for engines prone to overheating. This thermostat's hi-flow, balanced sleeve design facilitates a more rapid and uniform engine warm-up by increasing coolant circulation and preventing localized hot spots, particularly around the valve areas. By precisely controlling water flow and temperature, the 333 series minimizes thermal cycling and enhances the volume of coolant directed to the radiator, thereby improving overall cooling efficiency. This makes it an ideal choice for the 351 Cleveland engines found in performance vehicles like Mustangs and Panteras, which often require enhanced cooling capabilities. This thermostat is proudly made in the USA and is a genuine Robertshaw 333 series product. It is specifically designed for engines that utilize a brass bypass insert, such as many 351 Cleveland models. It's important to note that engines like the 400 and 351M, which have a cast bypass hole in the block, also require the 333 series thermostat, as they do not use the brass insert. Available temperatures include 160, 180, and 195 degrees Fahrenheit. A "substitute" version is also offered, which performs the same preheat function but features a resized bypass hole for greater temperature flexibility.